You are automatically exempt from the travel restrictions and can enter Australia (without obtaining an individual exemption) if you are:
Travelers planning to travel across Australian state borders should note that some Australian states also have domestic travel restrictions, border restrictions, and quarantine requirements in place. In the case of onward travel within Australia, travelers are advised to check in advance with their travel/accommodation provider.
Children under the age of 2 are exempt from presenting a COVID-19 test.
Travelers with proof of recovery from the virus within the last 90 days prior to boarding. Proof of a recent positive viral test and a letter from your healthcare provider or a public health official stating that you were cleared to travel.
More info at the CDC site
Travelers who did not get tested, are advised to stay home and self-quarantine for 10 days after travel.
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